Solar energy has been used for thousands of years as a heat and light source. In the last few decades, solar heating of water has become popular in a number of countries. In view of the increasing political and financial costs of oil, coupled with the deleterious environmental impacts thereof, many alternative energy sources are being developed. Solar energy may be concentrated and converted into electrical energy and, the electrical energy, in turn may be stored and/or fed into an electric grid.
The concentration of solar light energy provides many useful advantages, such as efficient use of photovoltaic (PV) cells. Conventional optics using focusing lenses, Fresnel lenses or convex mirrors of various shapes with sun-tracking systems are in use in many places. These are sometimes applied in industrial PV solar fields. Systems without sun-tracking are typically non-concentrating or low-concentrating systems.
In solar PV fields, most collecting systems pose shading constraints, which limit the maximal system array positioning density, that is, the positioning of plurality of sub-systems, one relative to the other. Conventional solar PV panels are often installed on flat roofs, but are typically set tilted and arranged in spaced-apart rows.
Fluorescent solar energy collectors, which guide light energy through a side surface of a collector have been proposed. However, such collectors have the disadvantages of low efficiency, stability and cost.
Holographic optical elements have been considered in the past for replacement of conventional lenses for directing light towards photovoltaic cells in solar panel systems.
At high latitudes, such as in Northern Europe, flat and compound parabolic reflectors, for low factor concentration, have been added to solar photovoltaic modules and more commonly to thermal modules (where lighting uniformity constraints are relaxed).
WO20080131561 discloses a solar energy system which uses a light-guide solar panel (LGSP) to trap light inside a dielectric or another transparent panel, which propagates the light to one of the panel edges for harvesting by a solar energy collector, such as a photovoltaic cell. This allows for very thin modules whose thickness is comparable to the height of the solar energy collector. This eliminates eliminating the depth requirements inherent in traditional concentrated photovoltaic solar energy systems.
In WO20090064701, a device comprising a light guiding layer, optically coupled to a photocell is described. A plurality of surface features are formed on one of the surfaces of the light guiding layer. The surface features can comprise facets that are angled with respect to each other. Light incident on the surface of the light guide is redirected by the surface features and guided through the light guide by multiple total internal reflections. The guided light is directed towards a photocell.
WO20090065069 discloses, a display device comprising a light collection film and a photovoltaic device disposed on an edge of the collection film. The collection film has a plurality of light-turning features for redirecting light between the front and rear surface of the collection film and the photovoltaic device. In some embodiments, a light source is also disposed on an edge of the collection film and emits light which is turned by the light-turning features toward the display.
There is still a need to provide efficient solar energy collection systems, which can be economically disposed in a solar field.